1. Field of the Invention
This invention is generally directed to a method of attaching orthodontic brackets to teeth and particularly to a method of direct or indirect bonding orthodontic brackets utilizing photopolymerizable bonding agent compounds having sufficient viscosity to retain a bracket in a desired position on the tooth after which a visible and/or ultraviolet light source is used to cure the polymers by directing the light from various angles between or relative to the base of a bracket and a tooth. The method is particularly adapted to permit bonding of brackets having solid or imperforate metal and ceramic or clear plastic or sapphire bases to teeth in less time than other known methods.
2. History of the Prior Art
Heretofore there have been various methods proposed for attaching orthodontic appliances to the surface of teeth. Many of the methods employed composites having somewhat lengthy setting times thereby requiring the orthodontist to retain a pressured grip on the orthodontic appliance or bracket during setting of the composite. Oftentimes, due to the long setting time, brackets would be shifted slightly and, therefore, not properly aligned when the composite began to set. Problems were also experienced in that excess composite would have to be removed from portions of the teeth adjacent the bracket which may have been coated by accidentally moving the bracket during its application. Such procedures were not efficient and required additional work for the orthodontist.
More recently, various polymers have been introduced which are more quickly cured. Many of these polymers may be subjected to heat, light or other radiant energy sources to induce a quick set of the polymer.
The problem encountered with use of some of the quick setting polymers has been that once the bracket has been coated with the polymer and placed against the tooth's surface, the polymer begins to cure so quickly that accurate bracket alignment is not always achieved. In such instances, the bracket must be removed from the tooth and the procedure repeated.
In the use of light or photo curable polymers, it has been necessary to enlarge the base of the orthodontic appliance or bracket and to make the base open or porous so that the polymer could be directly subjected or exposed through the holes or openings in the base to the waves of energy being used to polymerize the bonding agent. Absent the openings in the base of the brackets, it has heretofore been thought not possible to bond metallic or opaque bracket bases to teeth using a light curable polymer.
The use of larger bases for brackets not only results in an unattractive appearance but also increases the tooth surface are over which an orthodontic bracket is secured. Two problems are created by covering additional tooth surface. First, additional cleaning is necessary when the brackets are removed, and, second, there is an increased risk of damage to a larger area of a tooth's surface as the larger bracket bases make a greater area available in which food particles may be trapped increasing the likelihood of tooth decay in the area of the bracket.
A further problem with many prior art orthodontic bonding techniques has been that the brackets do not have sufficient bond strength to insure their placement over an extended period of time. Insufficient bond strength results in the necessity to replace various brackets during the course of a patient's treatment.
From the foregoing, it is obvious that orthodontists have been faced with several major problems. The first problem concerns the precise alignment of the brackets on the teeth which problem is directly affected by the length of time it takes the bonding agent to cure and the ability of the bonding agent to retain the bracket in a placed position prior to curing. Another problem directly concerns the failure of the bond between the bracket and the surface of a tooth. The need that various photopolymerizable bonding agents be visible or directly exposed through the base of the brackets to photo sources has presented a third problem in that known curing and bonding techniques have not been conducive to bond essentially any type of orthodontic brackets including imperforate and opaque brackets as well as clear plastic or sapphire brackets.
Some examples of the prior art include U.S. Pat. Nos. 3,745,653 to Cohl; 4,063,360 to Walker; 4,411,625 to Koblitz et al.; 4,435,160 to Randklev; 4,340,528 to Lee, Jr. et al.; 3,250,003 to Collito; 4,180,911 to Bullock; and 4,179,812 to Wright.